A new find of the enigmatic plant NematoplexusContribution by Hans-Jürgen Weiss, Rabenau (Germany)

Nematoplexus rhyniensis can immediately be recognized by
its peculiar anatomy. It is mainly made up of a tangle of wound tubes which
looks chaotic at first sight but surprisingly reveals more than one sign
of orderliness (Fig.1): The tubes are wound into a rather regular thread
which is always right-handed. The diameter of the thread lies between the
bounds of 0.08 and 0.12 millimeters, and the pitch of the thread seems to
equal its diameter.

There are a few more plants consisting of a felt of tubes, but none
of them has got its tubes wound into a thread. They are called nematophytes,
which means filamentous plants. They clearly differ from the various extant
types of filamentous algae. What they may have in common is some kind of
gel binding the tubes into a larger entity and keeping out floating debris
and aquatic creatures.

Fig.1: Nematoplexus rhyniensis, detail from
photo on website
University
of Aberdeen.
Copyright University of Münster.
Width of the photo: 0.35mm

Fig.2: Nematoplexus from own sample, natural
fracture face with coil fragments seen within the
the chalcedony, resembling those in Fig.1 except
for their size. Width of the photo 0.7 mm

Fig.3: Detail of this Nematoplexus specimen.
Width of the photo 0.42 mm.

Fig.4: Detail of this Nematoplexus specimen.
Width of the photo 0.35 mm.

Nematoplexus rhyniensis was described by A.G. Lyon on the basis
of only one chert sample of a rare variety without the usually abundant remains
of terrestrial plants. The sample presented here is of the same type, and
it is distinguished by the presence of the aquatic crustacean
Castracollis,
which has been repeatedly found recently in samples of the common chert type
with flooded terrestrial plants.

The present specimen of Nematoplexus (Figs.2-4) has been discovered
by inspecting the smooth surface of a chert layer fragment of 0.28kg. The
typical coil fragments are seen scattered over a patch of about 5 mm across.
Judging from the much larger specimen in Fig. 1 from Lyon (1961-62), this
patch is not representative of the whole. So it does not show structures
other than the smooth coiled tubes, in a more or less broken state.
As seen in Figs. 2-4, this specimen, too, shows the feature of right-handed
thread. By taking into account the foreshortening of the coils in these pictures,
it appears that the feature of pitch equalling thread diameter is also realized
here. What distinguishes the present specimen from the type specimen of
Nematoplexus rhyniensis is the conspicuously larger structure
size.

tube diameter [µm]

thread diameter [µm]

type specimen (Lyon 1961-62)

(7)-8-9-(10)

80-120

this sample

10-14

130-180

With the presently sparse fossil evidence of Nematoplexus, which
is apparently restricted to the type specimen and the sample described here,
it seems not justified to regard the bigger variety as a new species. This
may be reconsidered as soon as more finds revealing other details become
available.

H.-J. WEISS 2009
Figs. 2-4: photographs by C. KAMENZ

ReferencesA.G. LYON: On the fragmentary remains of an organism referable to the
nematophytales, from the Rhynie chert, Nematoplexus
rhyniensis. Trans. Roy. Soc. Edinburgh 65(1961-62), 79-87,
2 tables.Nematophytes
(University of Aberdeen).